1. Field of the Invention
The present invention relates to a fire monitoring system and fire sensors, which are capable of judging a fire by connecting a plurality of fire sensors to a receiver via a transmission line and then transmitting detection data from the plurality of fire sensors repeatedly in the predetermined order in response to respective instructions issued from the receiver. More particularly, the present invention relates to a fire monitoring system and fire sensors, which are capable of sending plural types of detection data selectively from the fire sensor by providing a plurality of sensors in the fire sensor.
2. Description of the Related Art
Conventionally, in the fire monitoring system which monitors a plurality of fire sensors concentratively by a receiver, the so-called multi-sensor type fire sensors each of which has functions of detecting smoke and heat are connected to the receiver via a transmission line.
According to such multi-sensor type fire sensor, when a smoke sensing circuit and a heat sensing circuit are provided such fire sensor, they can be switched according to the instruction issued from the receiver to operate individually (Unexamined Japanese Patent Publication (KOKAI) Hei 7-65263 (JP-A-7-65263)).
Therefore, the fire sensor can be operated as the smoke sensor or the smoke sensor according to the situations such as an installing location. In addition, if the fire is detected in the situation that the fire sensor is switched to the smoke sensing circuit, a false alarm can be prevented beforehand by switching the fire sensor to the heat sensing circuit to check the fire.
However, according to the fire sensor in which the smoke sensing circuit and the heat sensing circuit are switched according to the instruction issued from the receiver, there has been such a problem that a circuit configuration becomes complicated since a switching circuit is provided as a hardware to switch them. In addition, there has been another problem that, since two sensing circuits are switched so as to operate one of them and terminate the other, merely one of two sensing circuits can operate not to utilize plural types of detecting functions as a feature of the fire sensor.
Further, if the smoke sensing circuit and the heat sensing circuit are switched by allocating different addresses to respective sensing circuits, both sensing functions can be utilized by switching the address for the data request instruction. However, a plurality of addresses must be allocated to one fire sensor, nevertheless the maximum number of addresses which can be allocated to the fire sensors by the receiver is limited. As a result, there has been a problem that, since the number of address becomes insufficient, the number of the fire sensors which can be connected to the receiver is reduced.